# Update billing interval for a subscription contract

Updates the billing frequency (how often the customer is charged) for a subscription contract. This comprehensive operation recalculates billing dates, adjusts pricing, updates selling plans, and may also modify delivery intervals.

Key Features:
- Changes billing frequency while maintaining subscription continuity
- Automatically adjusts delivery interval when linked to billing
- Recalculates next billing date based on store settings
- Reprices all line items for the new frequency
- Finds and applies matching selling plans
- Handles anchor day adjustments for consistent billing
- Validates prepaid subscription constraints

Billing Interval Types:
- DAY: Daily billing (use with caution)
- WEEK: Weekly billing (e.g., every 1, 2, 3 weeks)
- MONTH: Monthly billing (e.g., every 1, 2, 3 months)
- YEAR: Annual billing

Validation Rules:
- Cannot set the same interval as current (no-op prevention)
- For prepaid subscriptions: billing interval must exceed delivery interval
- Example: Can't bill monthly if delivering weekly (would be paying for 1 delivery but receiving 4)

Next Billing Date Calculation:
The system uses sophisticated logic to determine the new billing date:
1. Starts from current or last successful billing date
2. Applies store timezone and order time preferences
3. Ensures date is in the future
4. Respects day-of-week preferences if configured
5. May keep current date if 'enableChangeFromNextBillingDate' is false

Side Effects:
- Delivery Interval: Updated if currently equal to billing interval
- Line Item Pricing: Recalculated based on new frequency multiplier
- Selling Plans: Finds and applies best matching plans for products
- Anchor Days: Updates billing anchor for consistent scheduling
- Email Notifications: Sends 'ORDER_FREQUENCY_UPDATED' to customer
- Activity Logs: Records both billing and delivery changes

Prepaid vs Pay-Per-Delivery:
- Pay-per-delivery: Billing and delivery intervals typically match
- Prepaid: Customer pays upfront for multiple deliveries
- This endpoint enforces prepaid logic to prevent undercharging

Authentication: Requires valid X-API-Key header

Endpoint: PUT /subscriptions/cp/api/subscription-contracts-update-billing-interval
Version: 0.0.1

## Query parameters:

  - `contractId` (integer, required)

  - `intervalCount` (integer, required)

  - `interval` (string, required)
    Enum: "DAY", "WEEK", "MONTH", "YEAR", "$UNKNOWN"

## Response 200 fields (application/json):

  - `get__typename` (string)

  - `id` (string)

  - `createdAt` (object)

  - `updatedAt` (object)

  - `nextBillingDate` (object)

  - `status` (string)
    Enum: "ACTIVE", "PAUSED", "CANCELLED", "EXPIRED", "FAILED", "$UNKNOWN"

  - `deliveryPrice` (object)

  - `deliveryPrice.amount` (object)

  - `deliveryPrice.currencyCode` (string)
    Enum: "USD", "EUR", "GBP", "CAD", "AFN", "ALL", "DZD", "AOA", "ARS", "AMD", "AWG", "AUD", "BBD", "AZN", "BDT", "BSD", "BHD", "BIF", "BYN", "BZD", "BMD", "BTN", "BAM", "BRL", "BOB", "BWP", "BND", "BGN", "MMK", "KHR", "CVE", "KYD", "XAF", "CLP", "CNY", "COP", "KMF", "CDF", "CRC", "HRK", "CZK", "DKK", "DJF", "DOP", "XCD", "EGP", "ERN", "ETB", "FKP", "XPF", "FJD", "GIP", "GMD", "GHS", "GTQ", "GYD", "GEL", "GNF", "HTG", "HNL", "HKD", "HUF", "ISK", "INR", "IDR", "ILS", "IRR", "IQD", "JMD", "JPY", "JEP", "JOD", "KZT", "KES", "KID", "KWD", "KGS", "LAK", "LVL", "LBP", "LSL", "LRD", "LYD", "LTL", "MGA", "MKD", "MOP", "MWK", "MVR", "MRU", "MXN", "MYR", "MUR", "MDL", "MAD", "MNT", "MZN", "NAD", "NPR", "ANG", "NZD", "NIO", "NGN", "NOK", "OMR", "PAB", "PKR", "PGK", "PYG", "PEN", "PHP", "PLN", "QAR", "RON", "RUB", "RWF", "WST", "SHP", "SAR", "RSD", "SCR", "SLL", "SGD", "SDG", "SOS", "SYP", "ZAR", "KRW", "SSP", "SBD", "LKR", "SRD", "SZL", "SEK", "CHF", "TWD", "THB", "TJS", "TZS", "TOP", "TTD", "TND", "TRY", "TMT", "UGX", "UAH", "AED", "UYU", "UZS", "VUV", "VES", "VND", "XOF", "YER", "ZMW", "USDC", "BYR", "STD", "STN", "VED", "VEF", "XXX", "$UNKNOWN"

  - `lastPaymentStatus` (string)
    Enum: "SUCCEEDED", "FAILED", "$UNKNOWN"

  - `billingPolicy` (object)

  - `billingPolicy.interval` (string)
    Enum: "DAY", "WEEK", "MONTH", "YEAR", "$UNKNOWN"

  - `billingPolicy.intervalCount` (integer)

  - `billingPolicy.anchors` (array)

  - `billingPolicy.anchors.cutoffDay` (integer)

  - `billingPolicy.anchors.day` (integer)

  - `billingPolicy.anchors.month` (integer)

  - `billingPolicy.anchors.type` (string)
    Enum: "WEEKDAY", "MONTHDAY", "YEARDAY", "$UNKNOWN"

  - `billingPolicy.maxCycles` (integer)

  - `billingPolicy.minCycles` (integer)

  - `deliveryPolicy` (object)

  - `lines` (object)

  - `lines.nodes` (array)

  - `lines.nodes.sellingPlanId` (string)

  - `lines.nodes.sellingPlanName` (string)

  - `lines.nodes.productId` (string)

  - `lines.nodes.sku` (string)

  - `lines.nodes.title` (string)

  - `lines.nodes.variantId` (string)

  - `lines.nodes.quantity` (integer)

  - `lines.nodes.customAttributes` (array)

  - `lines.nodes.customAttributes.key` (string)

  - `lines.nodes.customAttributes.value` (string)

  - `lines.nodes.lineDiscountedPrice` (object)

  - `lines.nodes.variantImage` (object)

  - `lines.nodes.variantImage.transformedSrc` (object)

  - `lines.nodes.variantTitle` (string)

  - `lines.nodes.currentPrice` (object)

  - `lines.nodes.discountAllocations` (array)

  - `lines.nodes.discountAllocations.discount` (object)

  - `lines.nodes.pricingPolicy` (object)

  - `lines.nodes.pricingPolicy.basePrice` (object)

  - `lines.nodes.pricingPolicy.cycleDiscounts` (array)

  - `lines.nodes.pricingPolicy.cycleDiscounts.afterCycle` (integer)

  - `lines.nodes.pricingPolicy.cycleDiscounts.computedPrice` (object)

  - `lines.nodes.pricingPolicy.cycleDiscounts.adjustmentType` (string)
    Enum: "PERCENTAGE", "FIXED_AMOUNT", "PRICE", "$UNKNOWN"

  - `lines.nodes.pricingPolicy.cycleDiscounts.adjustmentValue` (object)

  - `lines.nodes.taxable` (boolean)

  - `lines.pageInfo` (object)

  - `lines.pageInfo.hasPreviousPage` (boolean)

  - `lines.pageInfo.hasNextPage` (boolean)

  - `lines.pageInfo.startCursor` (string)

  - `lines.pageInfo.endCursor` (string)

  - `customerPaymentMethod` (object)

  - `customerPaymentMethod.instrument` (object)

  - `customerPaymentMethod.revokedAt` (object)

  - `customerPaymentMethod.revokedReason` (string)
    Enum: "AUTHORIZE_NET_GATEWAY_NOT_ENABLED", "AUTHORIZE_NET_RETURNED_NO_PAYMENT_METHOD", "FAILED_TO_UPDATE_CREDIT_CARD", "STRIPE_API_AUTHENTICATION_ERROR", "STRIPE_API_INVALID_REQUEST_ERROR", "STRIPE_GATEWAY_NOT_ENABLED", "STRIPE_RETURNED_NO_PAYMENT_METHOD", "STRIPE_PAYMENT_METHOD_NOT_CARD", "BRAINTREE_API_AUTHENTICATION_ERROR", "BRAINTREE_GATEWAY_NOT_ENABLED", "BRAINTREE_RETURNED_NO_PAYMENT_METHOD", "BRAINTREE_PAYMENT_METHOD_NOT_CARD", "PAYMENT_METHOD_VERIFICATION_FAILED", "THREE_D_SECURE_FLOW_IN_VERIFICATION_NOT_IMPLEMENTED", "MANUALLY_REVOKED", "FAILED_TO_RETRIEVE_BILLING_ADDRESS", "MERGED", "CUSTOMER_REDACTED", "TOO_MANY_CONSECUTIVE_FAILURES", "CVV_ATTEMPTS_LIMIT_EXCEEDED", "$UNKNOWN"

  - `deliveryMethod` (object)

  - `originOrder` (object)

  - `originOrder.name` (string)

  - `originOrder.fulfillmentOrders` (object)

  - `customer` (object)

  - `customer.displayName` (string)

  - `customer.firstName` (string)

  - `customer.lastName` (string)

  - `customer.email` (string)

  - `customer.phone` (string)

  - `discounts` (object)

  - `note` (string)

  - `billingAttempts` (object)


## Response 400 fields

## Response 401 fields

## Response 403 fields

## Response 404 fields

## Response 422 fields